Involvement of Oxygen-Derived Free Radicals in Chemical and Biochemical Degradation of Lignin

The formation of superoxide and hydroxyl radicals and their reactions during oxygen delignification are reviewed. It is concluded that: ▪ Oxygen delignification is a free radical process governed by the interplay between superoxide and the hydroxyl radical. ▪ Current process conditions favor carbohydrate degradation. ▪ Hydroxyl radicals may play an important part in the initial phase of microbial wood degradation. ▪ Oxygen delignification should be carried out under milder conditions: This would require the development of specific oxidation catalysts.